1. Field of the Invention
The present invention relates to substrate processing apparatus and a substrate processing apparatus for processing a substrate such as a semiconductor wafer.
2. Description of the Related Art
In a photolithography process in manufacturing a semiconductor device, a resist coating process for coating a resist on a wafer and a developing process for developing a coated resist after an exposure process. These processes are simultaneously performed by using a composite process system described in, e.g., U.S. Pat. No. 5,339,128. This system comprises a main handler for conveying a wafer, and is designed such that a wafer W is loaded by the main handler from a cassette station into a process section, the wafer W are exchanged between process chambers in the process section, and the above processes are performed.
A conventional handler has an arm section driven by three axes (Y axis, Z axis, and .theta. rotation axis), and the arm section a plurality of holding arms driven by only the X axis. All the 4-axis drive operations in the main handler are independently (individually) performed. For example, the arm section of the main handler moves in the Y-axis direction first, moves in the Z-axis direction, and then rotated at the angle .theta.. Finally, the holding arms move in the X-axis direction to receive a wafer.
In recent years, a demand for an increase in a throughput for a resist coating/developing process system is strong. For this reason, in order to answer this demand, the main handler must be operated at a speed as high as possible in a process section. However, since the 4-axis drive operations in the X-axis direction, Y-axis direction, Z-axis direction, and .theta.-rotation-axis direction are independently performed in the conventional main handler, the speed of the main handler operation is limited to a certain speed. The main handler performs sequential operations, e.g., the start of moving in the Y-axis direction, the end of the moving of the Y-axis direction, the start of moving in the Z-axis direction, the end of the moving of the Z-axis direction, the start of moving in the .theta.-rotation-axis direction, the end of the moving of the .theta.-rotation-axis direction, the start of moving in the X-axis direction, and the end of the moving of the X-axis direction. Therefore, a time from when the main handler reaches a target point to when the main handler receive a wafer is too long so that it is very difficult to increase the throughput.
In addition, when each drive system employs a high-speed drive mechanism to more increase the operation of the main handler, an excessive load acts on the mechanism, its durability and reliability may be degraded. In addition, when the operation speed of each drive system is increased, a noticeable amount of particle is generated, the wafer is contaminated by attaching particle on the wafer, and a yield may be decreased.
When a resist solution such as polyimide having a high viscosity is used in a resist coating process, even after a side rinse process in a coating device, the resist is not completely removed from the wafer peripheral portion, and the resist may be partially left on the wafer peripheral portion. When the residual resist is attached to the holding arms of the main handler, the wafer W is easily removed from the holding arms, and the wafer W cannot be smoothly conveyed. For this reason, the contact area between the wafer peripheral portion and the holding arms shall be minimized.
In a conventional method of conveying a wafer, independently of the distance between a main handler and a target point, the main handler is moved at a constant acceleration and a constant deceleration. For this reason, the distance between the main handler and the target point is long, the torque of a servo motor instantaneously, excessively varies at the start of the servo motor, vibration from the servo motor may be transmitted to the main handler. When the main handler vibrates, the contact state between the holding arms and the wafer W changes, and resist residue easily moves to the holding arms.
In a process using a resist solution having a low viscosity, it may be impossible to perform a side rinse process. For this reason, a wafer W on which a resist is coated is conveyed, the resist is attached to the holding arms due to vibration. This attached resist is dried soon and removed from the holding arms, thereby generating particles. In this manner, the wafer is contaminated by the particles, and a production yield is decreased.